[Intel-gfx] [PATCH] drm: Add rotation_property to mode_config and creating it

[Daniel Vetter]

On Tue, Jul 29, 2014 at 12:40:29PM +0300, Ville Syrjälä wrote:
> On Mon, Jul 28, 2014 at 08:47:22PM +0200, Daniel Vetter wrote:
> > On Mon, Jul 28, 2014 at 06:29:41PM +0300, Ville Syrjälä wrote:
> > > On Tue, Jul 15, 2014 at 05:43:37PM +0530, sonika.jindal at intel.com wrote:
> > > > From: Sonika Jindal <sonika.jindal at intel.com>
> > > > 
> > > > v2: Adding creation of rotation_property here.
> > > > 
> > > > Signed-off-by: Sonika Jindal <sonika.jindal at intel.com>
> > > > ---
> > > >  drivers/gpu/drm/drm_crtc.c |    3 ++-
> > > >  include/drm/drm_crtc.h     |    1 +
> > > >  2 files changed, 3 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> > > > index 787631e..49c0747 100644
> > > > --- a/drivers/gpu/drm/drm_crtc.c
> > > > +++ b/drivers/gpu/drm/drm_crtc.c
> > > > @@ -1299,7 +1299,8 @@ static int drm_mode_create_standard_plane_properties(struct drm_device *dev)
> > > >  					"type", drm_plane_type_enum_list,
> > > >  					ARRAY_SIZE(drm_plane_type_enum_list));
> > > >  	dev->mode_config.plane_type_property = type;
> > > > -
> > > > +	dev->mode_config.rotation_property = drm_mode_create_rotation_property(dev,
> > > > +			BIT(DRM_ROTATE_0) | BIT(DRM_ROTATE_180));
> > > 
> > > This might not make sense for other (!i915) hardware. And that's the
> > > reason why I had the driver create the property in the first place.
> > > 
> > > I think Daniel was thinking that we might want to expose all the bits
> > > regardless of what the hardware supports, but I don't like that idea.
> > > There are other properties (eg. alpha blending, csc stuff, etc.) that
> > > have the same problem of hardware supporting only a (potentially small)
> > > subset of the possible values. I'd rather we didn't make life harder
> > > for userspace when the kernel can already report that certain values
> > > will never work.
> > 
> > Well I'd like the property to be in some generic place so that fbcon can
> > unroate and that with the atomic stuff we can have rotation support in the
> > core structures. Which should help with argument checking.
> > 
> > But for rotation I don't think we should set it up in generic code, but in
> > i915. So the place where we keep it would be generic, the values would be
> > the sames, but the allowed set would differ depending upon platform or
> > driver.
> 
> That would still fail if all the planes on the same device don't support
> the same rotation flags. Eg. on i915 we would have this problem if we
> exposed the old video overlay as a drm plane. And it wouldn't be the
> first piece of hardware where I've seen this kind of thing.

Problem is still that I'd like to have a somewhat generic internal
representation available. We could punt this to atomic though by adding a
rotation field to the drm_plane_state structure. Which is more-or-less my
plan, but wouldn't work with Rob's approach.

Or we keep the property link only in drm_plane (and give drivers the
freedom to set up the underlying enum however they want to), but I'm not
sure whether our interfaces can cope with that.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch